These experiments were conducted with 10 hens raised on a gritless ration. After the disappearance of grit from the digestive tract (Fig. 2), 4 kinds of experimental food (5-10, 10-20, 20-30 mesh size grain, mash) and chewing-gum ball (3-7mm in diameter) containing BaSO., glass ball (3-8mm in diameter) and grit (10-20 mesh size) were given to them for the investigation of the place of deposition of the bolus as well as the movements of the gizzard by X-ray observations. And the movements was also observed from the changes of position of the silver wire attached to the outside of the gizzard (Fig. 1).
The results are as follows :
1) On feeding different types of food, the first boluses were swallowed directly into the gizzard, but the remainder lodged in the crop (Text-fig. 1). The directly swallowed amounts into the gizzard seemed to be few grams.
2) The place of deposition of the bolus was the same in any case of grain or mash feeding. And also the place was the same in any state of being hungry or full-fed (Figs. 3, 4, 5, 6).
3) Chewing-gum ball entered the crop (Fig. 7), glass ball and grit passed directly across the dorsal portion of the crop into the gizzard (Figs. 8, 9).
4) Almost all of the glass ball and grit never lodge into the crop even if in the full-fed state. The amount of grit intake is deemed just as much as necessary for the gizzard functions.
5) The gizzard sac at the relaxation pause present a cylinder shape inclining forward in the center of the abdominal cavity (Figs. 11, 12).
6) The gizzard sac was observed to present three waves (Text-fig. 2), namely two kinds of contractions and one relaxation. Firstly, the sac gradually began to incline backward and finally formed a reverse shape to the resting state (Figs. 14-16, 20-21). Secondly, it presented a round shape (Figs. 17,22), which occured rapidly and powerfully, and then followed the relaxation of resting pause (Figs. 18, 23). Mean cycle of movement occured at intervals of 20 sec.
7) The contraction of forming a reverse shape took longer interval than that of a round shape. The former occupied 8-10 sec. and the latter, 2-3 sec.
8) The silver wire attached to the outside of gizzard was not obviously influenced by the change in the shape and position of the gizzard throughout the contractions (Figs. 19-23). These facts suggest that the pattern of motility of the gizzard sac would not be peristaltic like the intestine, but they would be powerful contractions similar to those of the reticulum of ruminants.
9) It is very probable that the grinding action of the bolus in the gizzard would be carried out mainly at the stage of the round-shape contraction. And it is also suggested that the boluses would enter the gizzard just before the relaxation and pass into the duodenum at the round-shape contraction.